Preparation of lead arsenate



aroma KERRY, ItlA'lH'EW S. HOPKINS, AND CHARLES BAKER BERNHARQY, 0F REQDING,

fiENNSYIflLQNIA.

' PREPARATION OF LEAD ATE.

tance for use as an insecticide being sprayedupon the foliage of growing plants. As manufactured, the product may vary in its proportions of the two forms of arsenate dependent upon the quantities of the ingredients ,used and the conditions under which the manufacture is conducted.

It is well known that an arsenate of lead may be prepared by dissolving a salt of lead in water and adding to it a combining weight of arsenic acid- Alternatively litharge has been treated with an acid, preferably acetic, and the resulting lead salt precipitated with arsenic acid. While attempts have been made to produce the arsenate b the direct action of arsenic acid upon lit arge, the results are not satisfactory commercially due mainly. to the slowness of the reaction. Various means have been suggested to increase the speed of reaction by utilizing compounds or reagents operating in a cyclic or catalytic manner, for example the ordinary acids of industry nitrio, acetic, or the like. Such processes, however, are subject to the disadvantages resulting from the strength of these acids, the danger in handling them, difficulty and restrictions of their transportation and ex-= penses of manufacture.

relatively non-essential as a mixture of sul-.

fonic aclds obtained by the sulfonation of Specification of team latent.

Application filed July 28, 1921. Serial No. 489,156.

the commercial. grades of these hydrocarbons will act sill-actively. In addition, the lead arsenate produced bv the use of these reagents poi. U ph sical rcipiirements important for an insecticide, namely, large bulk, good dispersion, proper adherence to the foliage treated and effective insecticidal properties.

()ne mode by which the above invention may be carried out consists in sulfonating a commercial grade of an aromatic hydrocarbon such as ordinary naphthalene in the usual manner, removing any excess of sulfuric acid by suitable means such as by precipitation with a lead salt. Theclear liquid resulting after filtration or decantation consists of a mixture of various sulfonic acids of naphthalene and constitutes the catalyzer used in the process.

A charge of 700 pounds of litharge is placed in a tank and thoroughly agitated and kept in suspension in water. About 50 pounds of mixed sulfonic acids are then added, the. quantity to be used depending upon the speed of reaction required and the physical properties desired in the product. About 600 pounds of arsenic acid H AsO ,is then slowly added with con stant agitation. The temperature is raised to about 160 F. The mass gradually changes in color to white and the lltharge is converted to lead arsenate having a small excess of litharge, which latter may be re moved, if desired, by the addition of more arsenic acid. The resulting mass of lead arsenate, the lead salt of the sulfonic acid and water may then be washed by any of the usual methods and the lead arsenate pressed for use as pulp, or as powder after place of litharge, that a soluble arsenate may,

be substituted for the acid and that the mixed mono or polysulfonic acids which are obtained by the sulfonation of benzene, an-

iesses in a marked degree the i gmrphtbol, anthrax ox a-ritiufzwlho plo e above, Mao. A. zroprosem'lr y lmed willow; do

claims,

pound of Iood oiution nonzaio u;

arson. 111 2, 2 a sulfonatoia co pounc ,'dl'ooarbon.

SUlLliJliOll oontoi zmoonic in fihepresence. of a, sulfonotod compound of an aromatic hydrocsu'bcm The method of making Elam}. arsexmte which cons "'q 1 lead Ol'iid with arsenic mi .1 in. the pLo-sonoo of a sulfonated 00111130111161 of an mo no hyrocurbon.

4:. Tho nmhod of making; load rrsenato which. consisis in. i l'fiifli i)glfifld oxld with arsenio acid in the presence of a sulfona-tod 15 compound of mphthmlom.

5 The mofihod of making lead arsenate which consists in Heating an msolublo compound, of lead with arsenic acid in the presone-a of a" sulfonatod compound. of an aro mode hydroozn'bon.

The method of making lead o'rsenate which consists in treating an insoluble compound. of lead with arsenic acid in the pres once of a suifonatod compound of naph- I. The method of making load arsenate which consists in treating an insoluble compound of lead with a solution containing arsenic in the 'wrosonoo of a suifona iod compound of no (13" ale no.

stance contra-n 11g load and oxygen with sonic acid in tfae presence of a sul'fon'abod compound of naphthalene. I

The mefiood of nmkingji'oad arsonato vhioh c0215;

stones {3 iowo; lead and oxygen with a solution. wing arsenic an zhejp'resenco of am sad compound (I naphthalene.

I rmy whereof, Wm nfi'ixed 0m.

gnotures.

*QHN KIRBY.

v Li-FT. S HUPKHw BAKER 'BERNHART.

have hateunto he mthod of making lead arsenate, monsmfs 1n. troavtmg lead ornci wlth a,

1n the presence o treating on iosolubio 5 5%??? in treating an iiQfSOltibl d 9133- 

